1. Field of the Invention
This invention relates to a method for detecting and correcting a failure in the mounting of electronic circuit elements on printed circuit boards and an apparatus therefor, and more particularly to such a method and an apparatus which is adapted to carry out the classification of failed printed circuit boards each having any failure or imperfection faulty of the faulty mounting, misregistration of mounted electronic circuit elements with respect to the printed circuit board, a mistake of the mounting direction, the mounting of incorrect electronic circuit elements thereon or the like, from accepted printed circuit boards, and the transferring of the mounting failed printed circuit boards to a correcting station for correction of the failed printed circuit boards.
2. Description of the Prior Art
In a conventional manufacturing line for mounting electronic circuit elements (hereinafter referred to as "electronic parts" or "chips") on a printed circuit board or assembly board (hereinafter referred to as "substrate"), the correction of defective substrate (defined as a substrate having any imperfection or defect in the mounting of electronic parts thereon) is carried out in a manner such that a checker is operated to detect any mounting failure or imperfection in the mounting of the chips on the substrate upon each mounting of each chip thereon or after the mounting of all required chips thereon, and when it detects any mounting failure or imperfection, the defective substrate is removed from the line and collected in a chip receiver by human work. The so-collected defective substrate is then subjected to correcting operations at a separate correction station.
As can be seen from the foregoing, in the conventional mounting failure correcting system, the removing of a defective substrate from the manufacturing line must be manually carried out and it is required that an operator makes a mark at every failed portion of each defective substrate, so that the correction operation is highly troublesome and inefficient. Also, a failure in the mounting includes failure to mount any component, misregistration of mounted electronic parts with respect to a substrate, a mistake in the mounting direction, the mounting of incorrect electronic parts thereon and the like. However, it is highly inefficient to check or determine mounting imperfections of such various types by means of a single checker.
Also, as is apparent from the foregoing, in the conventional mounting failure correcting system, the checking of the mounting imperfection is carried out every substrate. This fails to improve the overall operation efficiency in the manufacturing line, even when the mounting of electronic parts on substrates is efficiently and continuously performed at a chip mounting station.
Further, the checking of the mounting failure is carried out by applying a fluorescent substance to portions of a substrate on which electronic parts are to be mounted and evaluating the radiating condition of the fluorescent substrate. Unfortunately, such procedure fail to precisely check the mounting failure.